Energy detector-based spectrum sensing is typically implemented using the periodogram. By including the time dimension, an image can be formed from consecutive periodograms referred to as the spectrogram. Such time-varying spectral representations are needed to address the dynamics of the signal environment in spectrum sensing applications. As indicated in reference [3] below, challenges associated with traditional implementations of energy detection schemes include: i) selection of the threshold for detecting primary users, ii) inability to differentiate interference from primary users and noise, and iii) poor performance under low signal-to-noise ratio (SNR) conditions.
In this sense, the spectrogram, which is referenced widely in the open literature, could be thought of as “prior art”. More appropriately, it would be the spectrogram combined with Welch's method of time averaging [4]. Also included in the prior art is the Adjustable Bandwidth Concept [1], which extends Welch's method to include the ability to average over frequency, and allows for operation on log-scaled amplitudes in the input spectrogram.